Behringer ultratone k450fx board problem

[Michaelpojas]

Hi guys. Please if you have diagram with that utratone k450fx.
I got a problem with sounding. If turn the volume up the speaker sound like rubbing then roaring.
I have tried replacing IC but same results.
But if the volume is 10 o'clock there is no problem. The sound is normal.
Please me. Is their any body knows how.